In current human and animal medical practice, there are numerous instances where therapeutic agents must be delivered to a specific organ or a tissue within the body. An example is the infusion of chemotherapy into a central vein on a recurring basis over a lengthy treatment period for widespread sites of malignant tumor. Without an access device for intravenous drug infusion, multiple vein punctures over a lengthy period would result in progressive thrombosis, venous sclerosis, and destruction of small diameter peripheral vessels. In other cases, it may be desirable to infuse chemotherapy to a localized malignant tumor site. It may be difficult or impossible to deliver an agent specifically to such a site on a regular repetitive basis without surgically implanting an access system. Similarly, repeated arterial access is occasionally needed for injection of an X-ray dye or contrast agent for diagnostic purposes. In other situations, there is a need to repetitively remove a body fluid for analysis from a remote body site. Finally, sensing and physiological measuring devices incorporated into small diameter catheters and optical fibers are increasingly being utilized for monitoring body processes and could be more easily implemented through a properly designed access device with an adequate internal diameter.
In prior medical practice, percutaneous catheters have been used to provide vascular or organ access for drug therapy or the withdrawal of body fluids. Although such systems generally perform in a satisfactory manner, numerous problems were presented by such therapy approaches, including the substantial care requirements of the patients, e.g. dressing changes with sterile techniques, a significant rate of infection of the catheter because of its transcutaneous position, and a high rate of venous thrombosis, particularly if the catheter was located within an extremity vein.
Implantable infusion devices or "ports" have recently become available and represent a significant advance over transcutaneous catheters. Presently available infusion ports have a number of common fundamental design features. The ports themselves comprise a housing which forms a reservoir that can be constructed from a variety of plastic or metal materials. A surface of the reservoir is enclosed by a high-density, self-sealing septum, typically made of silicone rubber. Connected to the port housing is an implanted catheter which communicates with a vein or other site within the patient where the infusion of therapeutic agents is desired. Implantation of such devices generally proceeds by making a small subcutaneous pocket in an appropriate area of the patient under local anesthesia. The implanted catheter is tunnelled to the desired infusion site. When the care provider desires to infuse or remove materials through the port, a hypodermic needle is used which pierces the skin over the infusion port and is placed into the port.
Although the presently available implantable infusion ports generally operate in a satisfactory manner, they have a number of shortcomings. Since these devices rely on a compressed rubber septum for sealing and since large diameter needles can seriously damage the septum, there are limitations in the diameter of needles which can be used to penetrate the septum. These diameter limitations severely restrict the opportunities provided by the port. In cases where it is desirable to infuse drugs using a flexible external catheter, the catheter must be fed through the needle that penetrates the septum. Such catheters have an extremely small inside diameter and, therefore, impose severe limitations on fluid flow rate and limit the types of fibers which can be introduced,
During prolonged infusion using a conventional port, the infusion needle is taped to the patient's skin to hold it in position. Conventional ports do not allow the needle to penetrate deeply into the port. Because of this, a small displacement of the needle can cause it to be pulled from the port. In cases where locally toxic materials are being infused, extravasation of such materials can cause local tissue damage which may require corrective surgery such as skin grafting or removal of tissue.
Presently available implantable drug infusion devices also have a significant size to provide an acceptable target surface area for the care provider who must locate the port and penetrate the septum with a needle. The port housing becomes bulky as the septum size increases since structure is required to maintain the septum in compression to provide self-sealing after the needle is removed. Moreover, presently available infusion ports are difficult to clear if thrombosis occurs within the port or within the implanted catheter since it is difficult, if not impossible, to feed a cleaning wire through the penetrating hypodermic needle in a manner which will clear the infusion device and the internal catheter. Present infusion ports also have a retained volume beneath the self-sealing septum which increases the volume of drug which must be administered to enable a desired quantity to reach the infusion site. This retained volume also poses problems when a care provider desires to successively deliver multiple drugs to the same infusion site which are incompatible when mixed. Additionally, when it is desired to withdraw blood through the port, the retained volume of the prior art infusion ports comprises an area where blood clotting can occur, thus interfering with future access to the site. And finally, for present infusion ports, there is a risk that the care provider attempting to pierce the port septum will not properly enter it, leading to the possibility of extravasation which can cause significant undesirable consequences as mentioned above.
The present invention relates to a family of implantable access ports which provide numerous enhancements over prior art devices. In accordance with this invention, an access port is provided which incorporates the funnel-shaped entrance orifice which narrows down to a reduced diameter passageway. Positioned within the passageway is an "articulating catheter valve or articulating valve", such as a multi-element leaflet valve assembly. The exit passageway of the port is connected to an implanted catheter which communicates with a desired site in the body.
One of the embodiments encompassed by the present application relates to an access port having a chamber for the retention of an antimicrobial or antibacterial fluid which aides in the prevention of infection in the area of the access port and particularly along the route of the percutaneously placed filament. Whenever a percutaneous route is provided the risk of infection is present. In the access port in accordance with this invention, the antibacterial solution can be made to slowly diffuse from the access port as an effective preventive measure against infection. In addition, the antibacterial fluid is permitted to coat the percutaneous filament as it is inserted and withdrawn from the port. The access port of this invention further provides a means for replenishing the antibacterial fluid chamber after the port is placed through a transcutaneous refilling instrument, through provision of a separate fluid reservoir, or both.
Access ports in accordance with the present invention provide a large diameter access pathway to a remote site within the patient. In some patient treatment-procedures prolonged infusions take place. Since the flow rate may be very low, there is a possibility that blood can backflow through the percutaneous catheter through the process of diffusion or under the influence of gravity. Patients can be traumatized or led to believe that the infusion system is operating improperly when blood is seen in the external catheter. As a means of precluded such reverse flow of blood through an external catheter, a blood stop device is provided in accordance with one aspect of this invention which is connected in-line with the external catheter close to the location of the access port. The device uses a filter media element having a filtration capability which traps red blood cells backflowing through the external catheter. Therefore, any red blood cells diffusing into the external catheter collect on a surface of the filter media element as opposed to traveling further in the external catheter. The blood stop of this invention can be used in connection with the various access ports described herein or in the related applications.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.